Picture-transmission system



Nov. 20; 1928; 1,692,232

T. T. BAKER PICTURE TRARSIQI SS IQN SYSTEM Filed Dec. 10, I925 Patented Nov. 20, 1928.

UNITED- STATES 1,692,232 PATENT OFFICE.

THOMAS THORNE BAKER, OF LONDON, ENGLAND, ASSINOR OF ONE-THIRD '10 CHARLES HENRY WATSON AND ONE-THIRD TO.FBEDERICK WILLIAM WATSON BAKER, BOTH OF LONDON, ENGLAND.

PICTURE-TBANSMISSION SYSTEM.

Application filed December 10, 1825, Serial No. 74,591, and in Great Britain December 11, 1924.

This invention relates to the telegraphic transmission of pictures, diagrams and other impressions and is concerned with apparatus for this purpose of the character comprising 8 at the transmitting station means for producing a spot of light, means enabling same to be progressively traced over a picture to be transmitted and a light-sensitive cell arranged to be affected by the rays reflected 10 from or passed through said spot and included in a circuit adapted for the emisison of signals, and at the receiving station apparatus adapted for receiving said signals and projecting light on to a sensitized sheet in accordance with the signals.

The object of the invention is to simplify the apparatus and enhance the speed and accuracy with which photographs, drawings and other impressed or recorded matter may be transmitted to distant receiving stations, whether by line or by radio telegraphic means.

According to this invention, apparatus of the character referred to is distinguished primarily by the receiver comprising a drum for the mounting of a sensitized sheet, a lamp under influence of the light-sepsitive cell of the transmitter, a casing containing said lamp and having an aperture through which the light from the lamp is directed on to a sensitized sheet on said drum, means to traverse said lamp casing in a fixed line parallel to the axis of said drum and means for rotatin the drum at a speed having predeter- 85 mined relation to the speed of traverse of said casing.

' For efiecting progressive ex osure of the sensitized sheet wrapped roun the drum at y the receiver station, it is very advantageous 40 to an port the casing and lamp on a small whee ed carriage which is fed along by the engagement of a kniie edge disc or wheel on the carriage engaging a fine worm or thread on the axle of the drum. It is advantageous to adopt for the lamp, a normal current which would over-run the lamp in the ordlnary way but which, owing to t e variation up and down of the current, does-no harm to the lamp but efiects a much more brilliant illumination than would otherwise be poss ble. In this way the reproduction is much am lified as compared with galvanometer meth s, and

' the so-ealled inertia of how-electric and seleniumeells is absent. wo lamps may be arranged in the casing, one being an emergency lamp. The latter may normally be masked by a shutter under relay magnet control, the relay being in circuit with the first lamp. Upon failure of the latter, the deenergizing of the relay magnet permits or brings about the immediate unmasking of the emergency lamp.

In the case of re dio-telegraphic transmission, the selenium cell at the transmitting station is advantageously arranged to afi'ect the grid circuit of the transmitting valve or valves and the lamp current at the receiving station may be varied by suitable connection with the plate circuit of a valve in the receiv: ing set. i

In order to enable the invention to be readily understood, reference is made to the accompanying drawing, which illustrates diagrammatically and by way of example suitable arrangements for the carrying out of these improvements, in which drawing Figure 1 is a diagram of a transmitter apparatus in which an ordinary photographic print wrapped round a c linder or drum reflects a spot of light whic is directed on to a photo-electric cell.

Figure 2 is a diagram of a receiving apparatus employing a lamp arrangement.

Referring to Figure 1, a is a drum around which a picture or ordinary photograph is wrapped, b is a lamp and c is a suitable lens or lens combination for concentratin the light on to a spot on the picture or p otograph. The light and lens may be enclosed in any suitable shield or casing. The light is reflected back from the picture to a suitably disposed prism d or the equivalent, adapted for directing the light on to a selenium or photo-electric cell e.

For radio telegraphic transmisison, the cell e is advantageously connected up in the grid circuit of the transmitting valve as shown by the drawing. Thus, the cell e may be made to act as a variable grid leak in connection with such valve, as by connecting its terminals with the terminals of the grid condenser.

The lamp 6, lens a, prism d and cell e may all be appropriately mounted upon a wheeled carriage, such as that described in my United States Patent No. 1,614,339, dated Jan. 11, 1927, this carriage being fed parallel with the axis of the drum a by means of an antifrictional screw feed. However, other means may be adopted for moving the spot of light progressively over the picture.

At the receiving station, a sensitized sheet is supported in a manner similar to that adopted at the transmitting station and, as seen in Figure 2, a lamp 7 is arranged within a casing g adapted for directing a spot of light on to the sensitized sheet. The lamp f and casing g are supported and moved in the same manner and at the same speed as the lamp Z), lens 0, prism d and cell c at the transmitting station. Suitable means for synchronizing the apparatus at the two stations is required as for example, the synchronizing means described in my aforesaid patent or the pendulum synchronizers described in my concurrent U. S. patent application Ser. N 0. 74.590 of even date herewith.

In the case of wireless transmission the lamp current is varied directly or indirectly by the plate current of the valve or lastvalve of a wireless receiving set.

It is advantageous to adopt for the lamp f a normal current which would over-run it in the ordinary way but which owing to the variation up and down of the current, does no harm to the lamp but effects a much more brilliant illumination than would be possible otherwise.

As seen in Figure 2, there may be two lamps f f within the casing g, the lamp f being normally masked by a shutter h under control of a relay magnet j which may be in circuit with the lamp Upon failure of the lamp f, the magnet j would be de-energized and thus permit, or bring about, the immediate unmasking of the lamp ting the shutter h to tilt to the dotted tion seen in Figure 2.

I claim In a receivin set for use in the telegraphic transmission 0 pictures, diagrams and other impressions in which signals from the transmitting station are produced by a spot of light progressively traced over the picture to be transmitted the rays from said spot being caused to act upon a light-sensitive cell which is included in a circuit adapted for the emission of signals, and the said signals are received by the said receiving set and utilized therein for varying the intensity of the light from an electric lamp, a second lamp, a movable mask normally operative for obscuring the light from said second lamp, electro-magnetic release means under control of the circuit of the first lamp and adapted for bringing about the removal of the mask from the second lamp when the first lamp fails, and light-directive means adapted for concentrating the light from either of the lamps on to a spot on a sensitive layer progressively advanced in relation to such spot simultaneously and synchronously with the advancement of the picture at the receiving station.

THOMAS THORNE BAKER.

posif, as by permit- 

